[issue2536] itertools.permutations docstring is misleading

[Daniel Diniz]

New submission from Daniel Diniz <ajaksu2 at users.sourceforge.net>:

Currently, Modules/itertoolsmodule.c lines 2471-2475 are:

PyDoc_STRVAR(permutations_doc,
"permutations(iterables[, r]) --> permutations object\n\
\n\
Return successive r-length permutations of elements in the iterable.\n\n\
permutations(range(4), 3) --> (0,1,2), (0,1,3), (0,2,3), (1,2,3)");

but that describes  behavior of itertools.combinations. The correct
example is in a comment on line 2254 of the same file:

'permutations(range(3), 2) --> (0,1) (0,2) (1,0) (1,2) (2,0) (2,1)'


I used "misleading" instead of "wrong" because the current docstring
does show a subset of the real output and could be said to be
incomplete. If that is the case, I suggest being explicit:

'permutations(range(4), 3) --> (0, 1, 2), (0, 1, 3), (0, 2, 1), (0, 2,
3), (0, 3, 1), (0, 3, 2), (1, 0, 2), (1, 0, 3), (1, 2, 0), (1, 2, 3),
(1, 3, 0), (1, 3, 2), (2, 0, 1), (2, 0, 3), (2, 1, 0), (2, 1, 3), (2, 3,
0), (2, 3, 1), (3, 0, 1), (3, 0, 2), (3, 1, 0), (3, 1, 2), (3, 2, 0),
(3, 2, 1)'

----------
components: Library (Lib)
messages: 64846
nosy: ajaksu2, rhettinger
severity: normal
status: open
title: itertools.permutations docstring is misleading
type: behavior
versions: Python 2.6

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<http://bugs.python.org/issue2536>
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